In recent years, researches on resins synthesized from raw materials derived from plants without using petroleum have been extensively carried on in order to cope with environmental problems such as global warming and exhaustion of fossil resources. In particular, researches on polylactic acid as a resin derived from plants have been carried on, and various products have been introduced to practical applications.
Thermoplastic resins typified by polylactic acid are generally classified into non-crystalline resins and crystalline resins, and the latter resins can be crystallized by a heat treatment. In the case of the crystalline resin, its heat resistance and mechanical properties such as stiffness and impact resistance can be improved by crystallization, so that the resin is desirably crystallized before use rather than used in a non-crystalline state. However, since no crystallizing process is required so far as necessary physical properties are satisfied even in an amorphous state, such a resin is desirably used in the amorphous state because productivity in molding processes is excellent.
A problem to be solved when the resin is used in the amorphous state is how to inhibit crystallization caused with time. The reason for it is that when the resin is crystallized with time, changes in physical properties and deterioration of transparency may occur compared with those just after molding.
Polylactic acid that is a typical plant-derived resin has heretofore been applied to films and bottles, and techniques for ensuring transparency without being crystallized have been reported. For example, a technique of adding a fatty acid to a polylactic acid resin has been reported (Japanese Patent No. 3852958) to obtain a polylactic resin composition excellent in parting property.
On the other hand, polyethylene furandicarboxylate is known as a plant-derived resin. The merit of polyethylene furandicarboxylate is to have excellent heat resistance compared with polylactic acid. However, an additive for inhibiting crystallization with time in polyethylene furandicarboxylate has not been yet known.